1. Field of the Invention
This invention relates to methods of producing oriented polymer material, particularly oriented film of high density polyethylene.
2. Description of the Prior Art
It is known that, by drawing a high density polyethylene sheet material at a temperature below its melting point to a draw ratio of, for example, 5:1 to 10:1, it is possible to produce an oriented polymer film having useful properties of transparency and high tensile strength in the direction of draw, as well as crease retention in some cases.
Commercially available films of this type, however, have gas barrier characteristics which are no better than those of the undrawn polyethylene sheet material.